Pipeline structure with a lining material, an end structure of said pipeline and a method for applying a lining material to a pipeline

ABSTRACT

A pipeline structure with a lining material wherein a hermetic outer tube is disposed at the inner surface of a pipeline, and an inner lining material is disposed at the inner surface of the outer tube, said inner lining being made of a rigid fiber-reinforced plastic wherein a thermosetting resin is reinforced by a fiber reinforcement material.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a novel structure and method forapplying a lining material to reinforce pipelines such as a gas conduit,a city water pipe, a sewage pipe, pipelines for laying telecommunicationcables or electric cables, and particularly, pipelines embedded in theground. More particularly, the present invention relates to a technicalmeans suitable for applying a lining material to a gas conduit orintermediate line with a working pressure of approximately 3 to 10kg/cm².

2. Background Art

A conventional method for applying a lining material to an undergroundpipeline comprises the steps of depositing a hermetic film on the outersurface of a tubular fiber reinforcement material composed of a tubularwoven or unwoven fabric, or a combination of tubular woven and unwovenfabrics superimposed one over the other to provide a lining material,applying a thermosetting resin liquid to the inner surface of the liningmaterial and impregnating the thermosetting resin liquid into thetubular fiber reinforcement material, inserting the lining material intothe pipeline while the lining material is being reversed under a fluidpressure, pressing the lining material against the inner surface of thepipeline under the fluid pressure, curing the thermosetting resin liquidso as to adhesively attach the lining material to the inner surface ofthe pipeline, and causing the thermosetting resin liquid and the tubularfiber reinforcement material to cooperate together to provide a rigidFRP (FIBER-REINFORCED PLASTICS) tube within the pipeline.

This method attempts to reduce the adhesive force between the liningmaterial and the inner surface of the pipeline so as to prevent thelining material from cracking as the pipeline is damaged, or the jointsfrom detaching due to earthquake or the like. This method also utilizeshigh strength fiber such as a glass fiber or an aromatic polyamide fiberon the circumference of the lining material so as to withstand internalor external pressure and insure a fluid path if the lining material isexposed as a result of damage to the pipeline (see U.S. Pat. No.5,164,237).

Such a lining method is effective in the case that the pipeline iscomposed of cast iron pipes or fume pipes, but is not sufficientlyeffective particularly when it is applied to a steel pipe such as a gasconduit with an intermediate working pressure of approximately 3 to 10kg/cm² (hereinafter, referred to as an "intermediate pressure A line").

The intermediate pressure A line uses carbon steel pipes which have ahigh strength and tenacity. These pipes are welded together to form along pipeline system. Bent pipes are welded to bent portions of thepipeline to provide an integral pipeline system. With such a pipelinesystem, if the ground is liquified or subjected to contraction due toearthquake, the resulting stress tends to be concentrated on the bentportions.

FIG. 3 shows the manner in which the bent portion of the intermediatepressure A line fractures. FIG. 3(a) shows a bent portion 2 of apipeline 1. When the ground contracts due to an earthquake or the like,the pipeline 1 is repeatedly extended and contracted in a longitudinaldirection. This results in a change in the angle of the bent portion 2.This change causes the bent portion 2 to be significantly deformed inthe direction in which it is bent and extended. If the bent angle α ofthe bent portion 2 increases, the bent portion 2 is urged into the pipe.If the bent angle a of the bent portion 2 decreases when the bentportion 2 is extended, a portion of the bent portion which has beenurged into the pipe is subject to extension. When the bent portion 2 islocally deflected to a substantial extent, a large crack 3 occurs withinthe bent portion 2 due to fatigue, as shown in FIG. 3(b).

In the case that a lining material 4 is adhered to the inner surface ofthe pipeline 1, the edge of the crack 3 is bent inwardly to producesharp burrs 5. These burrs 5 break the lining material 4 as shown inFIG. 3(c). Thus, damage to the pipeline 1 causes corresponding damage tothe lining material 4.

A cast iron pipe has a low tenacity. Thus, if a cast iron pipefractures, burrs 5 are rarely produced. Thus, a fluid path can bemaintained since the lining material 4 is free from damage. On the otherhand, a steel pipe has a high tenacity. Thus if a shock load is appliedto a steel pipe, it will not fracture as opposed to the cast iron pipe.However, a crack 3 is likely to occur when local stress is concentratedon the bent portion 2. The resulting burrs 5 will cause damage to thelining material 4.

An adhesive or a seal is applied to the end of the lining materialwithin the pipeline so as to prevent the entry of a fluid between thelining material and the pipeline. Normally, a metal ring is fit withinthe end of the lining material. The metal ring is extended to therebypress the end of the lining material against the inner surface of thepipeline (see JP, B, Sho. 60-41276).

With this treatment, however, the pipeline and the lining material issubjected to displacement if significant damage to the pipeline occurs.If the end of the lining material is displaced relative to the pipeline,the seal is damaged. A fluid then enters between the lining material andthe pipeline and may flow out of a portion of the pipeline thus damaged.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to overcome theproblems encountered in the prior art and to provide a structure andmethod for applying a lining material, which prevents the liningmaterial from being damaged by burrs which may occur when the bentportion of a pipeline composed of steel pipes is subjected to a crackand which insures the maintenance of a fluid path.

Another object of the present invention is to provide an improved endstructure which maintains the sealing integrity in the end of a liningmaterial if the lining material and a pipeline are displaced relative toeach other, thereby preventing fluid leakage.

The present invention provides a pipeline structure with a liningmaterial, characterized in that a hermetic outer tube 6 is disposed atthe inner surface of a pipeline 1, and an inner lining material 4 isdisposed at the inner surface of the outer tube 6 and made of a rigidFRP wherein a thermosetting resin 17 is reinforced by a fiberreinforcement material 12.

The present invention also provides a method for applying a liningmaterial to a pipeline, characterized by inserting a hermetic outer tube6 into a pipeline 1, then inserting into the outer tube 6 an innerlining material 4 wherein a fiber reinforcement material 12 isimpregnated with a thermosetting resin liquid, applying a fluid pressurewithin the inner lining material 4 so as to expand the inner liningmaterial 4, and curing the thermosetting resin liquid.

Preferably, the outer tube 6 is a tube made of polyethylene or nylon, ora tube to which a tubular unwoven fabric 9 is laminated.

It is preferred that the fiber reinforcement material 12 is reinforcedin its circumferential direction so as to retard expansion underinternal pressure, and that the radial expansion of the fiberreinforcement material 12 is small under the internal or workingpressure of the pipeline.

The present invention further provides an end structure for a pipelinelining material, characterized in that a flexible sleeve 22 has one endwhich fits within the end of an inner lining material 4 disposed withinthe pipeline 1; a metal ring 23a is positioned within the flexiblesleeve 22 and expanded to press the sleeve 22 and the inner liningmaterial 4 against the inner surface of the pipeline 1; that the sleeveis slackened at its center; and that a metal ring 23b is fit to theother end of the sleeve 22 and expanded to press the sleeve 22 againstthe inner surface of the pipeline 1.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, transverse sectional view of a pipeline with anassociated lining material according to the present invention;

FIG. 2(a) is a transverse sectional view, in part, of the wall structureof a pipeline with a lining material according to one embodiment of thepresent invention;

FIG. 2(b) is a transverse sectional view, in part, of the wall structureof a pipeline with a lining material according to another embodiment ofthe present invention;

FIG. 2(c) is a transverse sectional view, in part, of the wall structureof a pipeline 1 with a lining material according to a further embodimentof the present invention;

FIG. 3(a) is a side view showing a bent portion of a steel pipe with anlining material as known in the art;

FIG. 3(b) is a side view showing the manner in which a crack occurs inthe bent portion of a pipe as shown in FIG. 3(a);

FIG. 3(c) is a vertical sectional view of the steel pipe andschematically shows the bent portion with the lining material damaged byburrs which occur when the bent portion of the pipe as shown in FIG.3(a) is subject to a crack;

FIG. 4 is a side view of a machine for testing the deformation of apipeline with a lining material;

FIG. 5 is a vertical sectional view, in part, of one end of a pipelineand shows the end structure of a lining material made according to oneembodiment of the present invention; and

FIG. 6 is a vertical sectional view of a sleeve 22 associated with theend structure of the lining material of a pipeline according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to thedrawings.

FIG. 1 schematically shows, in transverse section, the wall structure ofa pipeline with an associated lining material according to the presentinvention.

Element 1 designates a pipeline which is made of steel. A hermetic outertube 6 is provided within the pipeline 1, but is not adhesively attachedto the inner surface of the pipeline 1.

FIG. 2(a) shows one form of the outer tube 6 wherein a tube 7 is made ofa plastic, such as polyethylene or nylon, which has a low gaspermeability. The outer tube 6 is composed only of the plastic tube 7.

FIG. 2(b) shows another form of the outer tube 6 wherein the plastictube 7 is laminated to the inner surface of a tubular unwoven fabric 9.FIG. 2(c) shows another form of the outer tube 6 wherein the plastictube 7 is laminated to the inner surface of a tubular woven fabric 8.

Referring next to FIGS. 1, 2(a), 2(b) and 2(c), 4 designates an innerlining material. In any of FIGS. 2(a), 2(b) and 2(c), the inner liningmaterial 4 is composed of a FRP layer 10 wherein a thermosetting resinis reinforced by a fiber reinforcement material 12, and a hermetic film11 attached to the inner surface of the FRP layer 10.

As shown in FIG. 2(a), the fiber reinforcement material 12 of the FRPlayer 10 includes a tubular woven fabric 15 composed of warps 13 andwefts 14, and high-strength filament yarns 16 extending around the outersurface of the tubular woven fabric 15 with high density. Thehigh-strength filament yarns 16 are interconnected by the warps 13 ofthe tubular woven fabric 15 so as to prevent undue expansion of theinner lining material due to internal pressure.

If the inner lining material 4 is subjected to undue expansion under theworking internal pressure, it is highly likely that the inner liningmaterial 4 would be damaged by burrs 5 which may occur when the pipeline1 is damaged due to an earthquake or the like. This is because the innerlining material 4 is constantly pressed against the inner surface of thepipeline 1 during use.

An unsaturated polyester resin or an epoxy resin is used as thethermosetting resin 17 which forms the FRP layer 10.

The inner lining material 4 has a circular section within the outer tube6. The inner lining material 4 is adhered to the inner surface of theouter tube 6 by the thermosetting resin 17. The outer tube 6 extendsalong the inner surface of the pipeline 1.

Next, in order to provide the pipeline with the inner lining material,the outer tube 6 is first inserted into the pipeline 1. The outer tube 6may be pulled into the pipe 1. Preferably, the reversible outer tube 6is inserted into the pipeline 1 while it is being turned inside outunder fluid pressure.

After the outer tube 6 has been inserted into the pipeline 1, the innerlining material 4 wherein the fiber reinforcement material 12 isimpregnated with the thermosetting resin liquid is inserted into theouter tube 6. It is also preferred that the reversible inner liningmaterial 4 is inserted into the outer tube 6 while it is being turnedinside out under fluid pressure.

The inner lining material 4 could be simply pulled into the outer tube6. However, the fiber reinforcement material 12 which is impregnatedwith the thermosetting resin liquid is exposed to the outer tube 6.Thus, it is difficult to pull the inner lining material 4 into the outertube 6 because the adhesive force of the thermosetting resin liquidretards the sliding movement of the inner lining material 4 relative tothe outer tube 6.

Reversion of the inner lining material 4 under fluid pressure duringinsertion eliminates the drag between the inner lining material 4 andthe outer tube 6. Advantageously, fluid or external pressure allows foran even distribution of the thermosetting resin liquid which has beenapplied to the inner lining material 4 before the inner lining material4 is reversed. Thus, the thermosetting resin liquid can be evenlyimpregnated into the entire inner lining material 4 when the innerlining material 4 is applied. Also, the fluid pressure causes the innerlining material 4 thus reversed to be expanded into a cylindrical shape.The cylindrical inner lining material 4 is then pressed against andapplied to the inner surface of the pipeline 1 through the outer tube 6.

First the outer tube 6 is inserted into the pipeline 1, and then, theinner lining material 4 is inserted into the outer tube 6. Thethermosetting resin liquid is cured while the inner lining material 4 isexpanded into a cylindrical shape under fluid pressure.

FIG. 5 shows the end structure of the inner lining material within thepipeline according to the present invention. Element 1 designates thepipeline. Element 4 designates the inner lining material applied withinthe pipeline 1. As shown in FIGS. 2(a), 2(b) and 2(c), the outer tube 6is disposed between the pipeline 1 and the inner lining material 4.

In this case, the outer tube 6 may be absent at the end of the innerlining material 4.

Element 22 designates a flexible sleeve. The sleeve element 22 is madeof rubber or a flexible plastic in which a thin woven fabric may beembedded. As shown in FIG. 6, the sleeve 22 has a small diameter portion22a at its one end which has a diameter substantially equal to the innerdiameter of the inner lining material 4, a large diameter portion 22b atthe other end which has a diameter substantially equal to the innerdiameter of the pipeline 1, and a taper portion 22c disposedtherebetween.

The sleeve 22 is attached to the end of the inner lining material 4 withthe taper portion 22c slackened as shown the broken line in FIG. 6. Thesmall diameter portion 22a of the sleeve 22 is fit within the end of theinner lining material 1. A metal ring 23a is engaged with the smalldiameter portion 22a and then, expanded so as to press the smalldiameter portion 22a of the sleeve 22 and the end of the inner liningmaterial 4 against the inner surface of the pipeline 1. The largediameter portion 22b of the sleeve 22 is engaged with the inner surfaceof the pipeline 1 outside of the inner lining material 4. A metal ring23b is fit within the pipeline 1 and then, expanded so as to press thelarge diameter portion 22b of the sleeve 22 against the inner surface ofthe pipeline 1.

OPERATION

According to the present invention, the inner lining material 4 iscomposed of the rigid FRP layer wherein the fiber reinforcement material12 is impregnated with the thermosetting resin 17. The inner liningmaterial 4 is not adhesively attached to the pipeline 1 since the outertube 6 exists between the inner lining material 4 and the inner surfaceof the pipeline 1.

If a crack 3 occurs in the bent portion 2 of the pipeline 1 as statedearlier, the inner lining material 4 may be inwardly deformed due to theresulting burrs 5. However, the inner lining material 4 would not bebroken by the burrs 5 since the inner lining material 4 is separatedfrom the pipeline 1. The inner lining material 4 will in no way bedamaged if the pipeline 1 is damaged.

The inner lining material 4 can be swung within the pipeline 1 under aworking pressure, particular when the inner lining material 4 has anouter diameter less than the inner diameter of the pipeline 1. If thecrack 3 occurs, the inner lining material 4 is easily moved away fromthe burrs 5 and will in no way be damaged.

The outer tube 6 is composed of the tubular unwoven fabric 9 or thetuber woven fabric 8 laminated with the tube 7. The tubular unwovenfabric 9 or the tubular woven fabric 8 protects the tube 7 as well asthe inner lining material 4 from being damaged by the burrs 5. Thiseffectively prevents fluid leakage.

The tube 7 of the outer tube 6 is made of a material which has a low gaspermeability, such as polyethylene or nylon. Thus, no gas will leak fromthe tube.

As shown by the solid line in FIG. 5, the end of the inner liningmaterial 4 is hermetically sealed against the inner surface of thepipeline 1. The end of the inner lining material 4 is pressed betweenthe metal ring 23a and the pipeline 1 so as to prevent the entry of afluid between the inner lining material 4 and the pipeline 1.

If the pipeline 1 is broken or opened due to an earthquake or the like,the inner lining material 4 is separated from the pipeline 1 withoutsuffering damage and remains in the form of a rigid tube. As a result,the end of the inner lining material 4 is displaced relative to thepipeline 1 or moved to the left as shown by broken line in FIG. 5.

The sealing integrity may be lost when displacement between the innerlining material 4 and the pipeline 1 takes place. The small diameterportion 22a of the sleeve 22 is moved with the inner lining material 4whereas the large diameter portion 22b is fixed to the pipeline 1. Theslackened portion is thus extended as shown by broken line in FIG. 5.Under the circumstance, the sleeve 22 prevents the entry of a fluidbetween the pipeline 1 and the inner lining material 4 and the leakageof the fluid from the broken portion of the pipeline 1.

Again, according to the present invention, the sleeve 22 is moved fromits slackened condition to an extended condition to accommodate therelative displacement between the end of the inner lining material 4 andthe pipeline 1 when the pipeline 1 is subject to fracture due to anearthquake or the like. Thus, the sleeve 22 maintains sealing integrityat the end of the inner lining material 4 and prevents fluid fromentering between the pipeline 1 and the inner lining material 4 andfrom, flowing out of the pipeline 1 through its broken portion.

EXAMPLE

The pipeline 1 takes the form of an intermediate pressure A gas conduit(inner diameter of 204.7 mm and working pressure of 10 kg/cm²).

Details of the outer tube 6 are as follows.

Example 1 (polyethylene tube)

A low density polyethylene tube having an outer diameter of 200.0 mm, athickness of 0.45 mm, a tensile strength of 160 kg/cm², and anelongation of 700% when broken.

Example 2 (unwoven fabric)

A tubular unwoven fabric having an inner diameter of 188.6 mm, athickness of 4.9 mm when a load of 500 g/cm² is applied, a density of0.18, extension strength of 25 Kg/cm and an elongation of 120% whenbroken. The tubular unwoven fabric is made of polyester and laminatedwith the polyethylene tube of Example 1.

Comparative Example (without outer tube)

No outer tube 6 is employed.

To make the fiber reinforcement material 12 which forms the FRP layer 10of the inner lining material 4, there is provided 640 lengths of warps13, each including three polyester filament yarns having a thickness of1,100 d and two polyester span-like filament yarns having a thickness of1,000 d. 30 lengths of wefts 14 each includes two polyester filamentyarns having a thickness of 1,000 d and are picked up over a span of 10cm so as to provide a tubular woven fabric 15. 15 lengths of yarns, eachincluding aramide filament yarns having a thickness of 1,500 d, arepicked up over a span of 10 cm and are wound around the outer surface ofthe tubular woven fabric 15. A plurality of polyester span-like filamentyarns or fastening yarns have a thickness of 1,000 d and are used tointerconnect the yarns at thirty-two points.

The fiber reinforcement material 12 has a weight of 1,090 g/m, a width,in flattened state, of 290 mm, a thickness of 2.6 mm, a longitudinalstrength of 330 kg/cm, and a breaking pressure of 23 kg/cm². The outerdiameter of each of the pipeline 1 used in Example 1, Example 2 andComparative Example under a working pressure (10 kg/cm²) is as follows.

Example 1 205.1 mm

Example 2 197.1 mm

Comparative Example 206.9 mm

In the following tests, the thermosetting resin 17, which forms the FRPlayer 10 of the inner lining material 4, is made of epoxy resin.

DEFORMATION TEST

The pipeline 1 used in Example, 1, Example 2, and Comparative Examplehas a length of approximately 2 m and is provided with a lining. Thebent portion 2 has an angle of 22.5 degrees. The pipeline 1 is tested bya test machine shown in FIG. 4.

In FIG. 4, 1 designates the pipeline with the bent portion 2. A liningmaterial is applied to the inner surface of the pipeline used in Example1, Example 2, and Comparative Example. 18 designates a stationaryfixture on which a movable fixture 19 is slidably mounted. The pipeline1 extends between the stationary fixture 18 and the movable fixture 19.20 designates a center hole jack which includes an operating rod 21adapted to move the movable fixture 19 along the stationary fixture.

After the pipeline 1 is mounted to the machine, an air under a pressureof 10 kg/cm² is injected into the inner lining material 4. The centerhole jack 20 is then operated to reciprocatingly move the movablefixture 19 to the left and right by 50 mm and 100 mm from its initialposition so as to bend the bent portion 2 of the pipeline 1. The movablefixture 19 is reciprocated until a crack occurs in the pipeline 1, andthe air under pressure leaks from the pipeline 1. Measurement is takenat one-eighth of each reciprocating movement of the movable fixture 19.

The result of the test is shown in Table 1.

                  TABLE 1    ______________________________________           OUTER                       AIR           TUBE    MOVEMENT   CRACK    LEAKAGE    ______________________________________    EXAMPLE 1             POLY-      ±50 mm 25/8   55/8             ETHYLENE  ±100 mm 15/8   36/8             TUBE    EXAMPLE 2             UNWOVEN    ±50 mm 25/8   73/8                       ±100 mm  6/8   >10    COMPAR-  NONE       ±50 mm 25/8   55/8    ATIVE              ±100 mm 15/8   15/8    EXAMPLE    ______________________________________

TENSILE TEST

Two straight pipes having a length of 900 mm are arranged in series andspaced 100 mm apart from each other. A lining material used respectivelyin Example 1, Example 2 and Comparative Example extends through thepipes. A pressure of 1 kg/cm² is applied to cure the thermosetting resin17.

The ends of the inner lining material 4 within the pipes are treatedaccording to the present invention. Thereafter, the ends of the pipesadjacent to opposite ends of the inner lining material 4 are closed. Awater pressure of 10 kg/cm² is applied within the inner lining material4. One of the pipes is fixed, whereas the other pipe is pulled. Load ismeasured when the distance between the pipes increases by 10 mm.

DAMAGE RESISTANCE TEST

The pipes with the lining material used in the tensile test are spaced110 mm apart from each other with an internal pressure of 10 kg/cm². Achisel is brought into contact with the surface of the inner liningmaterial 4 between the pipes. The chisel includes a tip having an angleof 45 degrees. The chisel is then urged into the inner lining material 4by 3 mm. In this state, the chisel is moved along the length of theinner lining material by 100 mm and reciprocated ten times. The numberof movement of the chisel is measured until the inner lining material 4is broken to thereby cause the water under pressure to be ejected fromthe inner lining material 4.

In the event that the sealing integrity of the inner lining material 4is still maintained after the chisel is reciprocated ten times, the sametest continues, but the chisel is more deeply pressed into the innerlining material progressively by 2 mm. The test is repeated until theinner lining material 4 is broken to thereby cause ejection of the waterunder pressure.

TEST FOR DETERMINING THE FOLLOWABILITY OF THE INNER LINING MATERIAL ASTHE PIPES ARE DISPLACED

Two pipes have a length of 900 mm and are serially arranged in anend-to-end fashion. A lining material used respectively in Example 1,Example 2 and Comparative Example is applied within the pipes. The twopipes are separated by 100 mm while a pressure of 10 kg/cm² is beingapplied within the inner lining material. At this time, measurement istaken to determine a maximum load. Also, the extent of extension of theinner lining material 4 is measured when the inner lining material 4fractures.

The results of the tensile test, damage resistance test, andfollowability test are shown in Table 2.

                  TABLE 2    ______________________________________                                      COMP.    ITEM        EXAMPLE 1  EXAMPLE 2  EXAMPLE    ______________________________________    OUTER TUBE  PE TUBE    UNWOVEN    NONE                           FABRIC    TENSILE TEST                5.10 t     3.14 t     8.54 t    RESISTANCE TO    DAMAGE    CHISEL DEPTH     3 mm       10th TIME  10th TIME  3rd TIME     5 mm       10th TIME  10th TIME     7 mm        5th TIME  10th TIME     9 mm                  10th TIME    11 mm                  10th TIME    13 mm                   9th TIME    FOLLOW ABILITY    MAX         100 mm     100 mm     41 mm    ELONGATION    FRACTURE    NO         NO         YES    MAX LOAD    10 t       11 t       18 t    ______________________________________

From the test for determining the followability of the inner liningmaterial as the pipes are displaced, it is found that the inner liningmaterial follows with displacement of the pipes. This is becauseaccording to the present invention, the inner lining material is notadhesively attached to the pipes. Thus, the inner lining material 4 willin no way fracture when the pipes fracture.

From the damage resistance test, it is found that the inner liningmaterial of the present invention has an excellent resistance to damage.Thus, the inner lining material 4 will in no way be damaged by burrswhich may occur when the pipeline 1 is subject to fracture. It alsoprevents fluid leakage.

It will readily be assumed that in Example 2, the unwoven fabricprotects the inner lining material 4 to provide an improved resistanceto damage. Also, in Example 1, the polyethylene tube or outer tube 6 perse is not related to the resistance to damage, but has significantlybetter resistance to damage than the comparative example.

As is clear from the result of the tensile test, the lining material ofthe comparative example is tensed upon application of substantial loadsto the lining material. This is due to the fact that the lining materialcan not readily be separated from the pipeline since the lining materialis adhesively attached to the pipeline. Accordingly, the lining materialis likely to be broken by the burrs 5 when the bent portion 2 of thepipeline 1 is subject to fracture 3.

Conversely, the lining material of Example 1 is not under tension sinceit is separated from the pipeline. Accordingly, the lining material willbe inwardly deformed if the burrs 5 urges the lining material. Thelining material will in no way be broken by the burrs 5. It will beunderstood that better resistance to damage is obtained when the liningmaterial is not adhered to the pipeline.

Deformation test is made to the pipeline 1 which has a bent portion 2and a lining material. From this test, it is found that the number ofmovement until fluid leakage occurs after the pipeline 1 cracks isgreater in Examples of the present invention. Thus, the lining materialinsures a fluid path if the steel pipe is damaged due to earthquake orthe like.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A pipeline structure with a lining material whichcomprises:a pipeline a hermetic outer tube non-adhesively disposed atthe inner surface of the pipeline, and an inner lining made of a rigidfiber-reinforced plastic comprising a thermosetting resin reinforced bya fiber reinforcement material, said inner lining being disposed at theinner surface of said outer tube.
 2. The pipeline structure with alining material according to claim 1, wherein the hermetic outer tube ismade of a material selected from the group consisting of polyethylene,nylon, and polyethylene or nylon to which a tubular fabric is laminated.3. The pipeline structure with a lining material according to claim 1,wherein said fiber reinforcement material is made of a material whichhas a low coefficient of radial expansion upon application of a workingpressure of the pipeline.
 4. The pipeline structure with a liningmaterial according to claim 1, wherein the pipeline is made of steel. 5.The pipeline structure with a lining material according to claim 1,wherein the inner lining is adhesively disposed at the inner surface ofsaid outer tube.